Recovery and purification of hydrocarbon oil



M. R. MANDELBAUM ,Filed Nov. 16, 1955 RECOVERY AND PURIFICATION OF HYDROCARBON OIL Nov. 23, 1937,.

INVENTOR MALVIH l2. MAHDELBAUM wwfl M ATTORNEY Patented Nov. 23, 1937 UNITED STATES PATENT OFFICE RECOVERY AND PURIFICATION OF HYDRO- CARBON OIL Application November 16, 1933, Serial No. 698,327

2 Claims.

the like, but may be employed for the purpose of recovering and refining other low-boiling hydrocarbon oils such as cracked gasoline and naphtha derived from cracking petroleum oils.

My invention has for an object the provision of a process whereby a refining operation may be carried out as adjunct to and in conjunction with a stripping operation in which low-boiling hydrocarbon oils are removed from relatively highboiling oil previously employed for the purpose of absorbing them from gases or gaseous mixtures containing the same. 7

My invention has fora further object the provision of a vapor phase refining process for treating low-boiling hydrocarbon oils that is es- 2 pecially advantageous where the vapors to be treated include large quantities of steam, and

particularly where a substantial amount of the hydrocarbons present in the vapors have a boiling point or boiling points below that of water.

My invention has for further objects such additional improvements in operative advantages and results as may hereinafter be found to obtain.

In removing low-boiling hydrocarbons such as benzol and gasoline from gaseous mixtures or gases containing them, it is common practice to scrub the gases with a relatively high-boiling absorbent oil and to remove the low-boiling hydrocarbons from the thereby enriched absorbent oil by convective distillation, steam being the preferred convection medium.

Thus, in removing benzol and analogous aromatic light oils from coke-oven gas, it is the common practice in the United States to scrub the gas with a relatively high-boiling gas oil, commonly known as straw oil, or with other relatively high-boiling hydrocarbon oil, which is substantially non-volatile upon steam distillation, andthen to subject the thereby enriched absorbent oil to steam distillation in a column still, the stripped wash oil being cooled and recirculated for further treatment of gas, while the vapors liberated in the stripping still are separately removed and condensed.

It has been proposed to effect the refining of light hydrocarbon oils such as gasoline and benzol by means of contact in the vapor phase with solid adsorbent materials having the power of selectively polymerizing unstable and undesirable unsaturated hydrocarbons to higher-boiling polymers readily removable by fractionation from the desired low-boiling hydrocarbon product. In the instances in which this process has been employed, however, hydrocarbon vapors have been treated in the absence of large quantities-of steam, and it has been a well accepted practice to permit a controlled amount of condensation to take place during the treating stage in order to provide a liquid medium for washing the bed of absorbent material to remove polymers therefrom and also to effect some condensation of the polymers.

I have found, however, that when the hydrocarbon vapors contain large amounts of steam, as is true when steam distillation is resorted to for removing the low-boiling hydrocarbons from the relatively high-boiling absorbent oil, the operation of the so-called clay-treating stage at a condensing temperature inevitably results in the condensation of large quantities of water. This is ordinarily undesirable for the reason that it interferes with the action of the adsorbent material and reduces the eificiency of the same and the extent of polymerization. Thus, in the presence of large quantities of steam, polymers formed in the bed of treating material tend to be low in fluidity, by reason of the fact that the steam. (by convection effect) prevents condensation of the oil which would normally dilute or dissolve the polymers and maintain them in a free-flowing condition. This, in turn, causes the polymers to build up in the bed of adsorbent material and greatly reduces the efliciency of the latter.

According to my invention, I subject the mixed vapors of low-boiling hydrocarbons and steam,

' such, for example, as those resulting from the steam distillation of an absorbent oil previously employed to remove low-boiling hydrocarbons from gases containing them, to contact with a solid adsorbent material effective to selectively promote polymerization of unstable unsaturated hydrocarbons to higher boiling products, at a temperature above the condensing point of steam and in the presence of a relatively high-boiling hydrocarbon oil that is substantially non-volatile under the conditions of treatment, that is to say, substantially unafi'ected by the steam and the temperature.

Preferably, although not necessarily, the vapors are treated by passing them through a bed of solid adsorbent material in a downward direction and the bed is simultaneously supplied with a suitable quantity of relatively high-boiling solvent oil for the purpose of washing the bed and removing polymers therefrom. The bed of adsorbent material is contained in suitable apparatus which may be insulated or otherwise adapted to be maintained at a temperature somewhat above the condensing point of steam. The solvent oil and the treated vapors are ordinarily separately removed and the latter are condensed. The condensed, low-boiling hydrocarbons are separated from the aqueous condensate. The low-boiling hydrocarbons are preferably fractionated or redistilled to separate polymers that may be contained therein, and may in fact be given any further treatment which is desired.

In a preferred embodiment, the relatively highboiling oil employed in the treating stage may be similar or identical in character to the absorbent oil, and where, as in benzol-recovery plants, the absorbent oil is recirculated over the gasand through a stripping still in a closedcycle, makeup oil ordinarily required to offset mechanical losses with or without additional make-up oil, as required, may be. employed in the treating stage, the resultant mixture of oil and polymers being added to, the recirculating body of absorbent oil to offset mechanical losses.

According to another aspect of my invention, the vapors of steam and low-boiling hydrocarbons leaving the stripping still may be passed through a distilling column maintained at a temperature above the condensing point of steam and wherein the vapors are subjected to contact with a. slurry of solid adsorbent material and relatively highboiling oil, the vapors being separately removed for treating the vapors are those which have the power of selectively polymerizing unstable and undesirable unsaturated hydrocarbon constituents to relatively high-boiling polymer products, and includes both natural and activated adsorbent earths, clays and other cellular materials. As specific examples of materialsuseful in the process I may cite fullers earth, bentonite, infusorial earth and kieselguhr.

In order that my invention may be clearly set forth and understood-I now describe, with reference to the accompanying drawing, apzeferred form and manner in which my invention may be embodied and practiced, without, however, limiting my invention to the details of the illustrative example or examples given hereinbelow.

In the drawing Fig. 1 is a more or less diagrammatic elevational view of apparatus for removing low-boiling hydrocarbon oil from gases containing the same and for refining the oil in accordancewith my present invention; and

Fig. 2 is a similar view of a modified form of a portion of the apparatus shown in Fig. l.

Similar reference numerals designate similar parts in both of the views of the drawing.

By way of example, my process will be described hereinbelow with reference to the recovery and refining of benzol and analogous light oils from coke-oven gas or the like, it being understood that my invention may be employed for the recovery of refined gasoline from refinery gases.

Referring now to the drawing and more particularly Fig. 1, coke-oven gas or other gas containing aromatic lightoils is introduced to a scrubber I, which is' preferably interiorly provided with suitable gas-and-liquid contact means (not shown), through a conduit 2 and then passes upward through the scrubber I in countercurrent to a stream of heavy gas oil, straw oil, or other relatively high-boiling hydrocarborpoil introduced to the scrubberl through an inlet line 3. During countercurrent contact of the gas and oil, the latter absorbs low-boiling hydrocarbon constituents such as benzol, toluol and xylols from the gas, and the scrubbed gas then passes out of the scrubber I through an outlet 4 for further use or distribution as desired.

The enriched absorbed oil collects in the bottom of the scrubber I and is removed therefrom through a conduit 5 and delivered by means of a pump 6 to an oil-to-oil heat exchanger 1 where it is heated; and thence through a conduit 8 to a preheater 9 where the temperature of the enriched oil is further increased, preferably by indirect contact with steam or other heating medium. The preheated enriched oil then passes through a conduit II to a wash-oil stripping still I2 of conventional type, wherein it is convectively distilled by means of steam introduced to the bottom of the still I2 through a steam inlet I3. As the absorbent oil flows down through the still I2 in countercurrent to the rising flow of steam, it is convectively distilled and stripped of its lowboiling hydrocarbon content previously removed from the gases in the scrubber I. The stripped or lean absorbent oil then passes out of the bottom of the still .I 2 through a conduit I 4 and is delivered by means of a pump I5 through a conduit I6 to the oil-to-oil heat exchanger 1 where it gives up a portion of its heat to the relatively cold oil leaving the scrubber I. The partly cooled absorbent oil then passes through a conduit I I to a cooler I8 where it is still further cooled to approximately atmospheric temperature and then returns through the inlet 3 to the scrubber I.

While, in the instance illustrated in the drawing, I have shown-a conventional recirculating cycle for the absorbent oil, it will be obvious to those skilled in' the art that the nature and disposition of the various heat exchangers, coolers and preheaters may be'varied in accordance with individual requirements.

The mixture of steam and liberated lowboiling hydrocarbonvapors leaving the still I2 passes through a vapor line 2| to a treating tower 22 adapted to contain a body 23 of solid adsorbent material such as fullers earth. In the 'instance illustrated in the drawing, the tower 22 is provided with insulation 24, but other means may be provided for maintaining the temperature of the bed 23 above the condensing point of the steam present in the vapors passing through the tower. a

The actual temperature may, however, be somewhat below the actual boiling points of the low-boiling hydrocarbon materials which have boiling points above that of water by reason of the presence of large quantitiesof steam and the convective distillation effect realized. For example, when the tower 22 is maintained at a temperature merely sufiicient to prevent condensation of steam, compounds suchas toluene and xylenes, although below their theoretical condensing temperatures, will not be thrown down in substantial amounts by reason of the convective distillation effect'of the steam. The actual temperature of the clay-tower 22, therefore, need not be above the boiling point of all of the constituents of the vapors.

For the purpose of removing polymers from the clay bed 23 and maintaining the same in a 'an outlet 3| for steam or other heating fluid, and

thence through a line 32 and a distributor 33 into the interior of the tower 22.

The oil thus employed should, as has been indicated hereinabove, have a boiling point range sufiiciently high to remain substantially nonvolatile in the tower 22. A suitable oil may thus be similar in character to, or identical with the oil employed as an absorbent in the cycle of the scrubber l and stripping still I2. Thus, I may employ a so-called straw oil, which is a gas oil commonly employed as a benzol absorbent. A typical straw oil has a boiling point range offrom about 450 F. to 600 F., and a specific gravity of the order of 35 A. P. I.

The oil thus introduced, due to its relativel high boiling point, remains substantially unaffected by the steam and extracts polymers from the bed 23 asthey are formed. It is then removed from the bottom of the tower 22 through a sealed line 34 having a valve 35. Where desired, this oil may be withdrawn from the system through a branch conduit 36 having a valve 31, or where the oil is similar in character to the absorbent oil employed in the scrubber I and may constitute make-up oil for the absorbing cycle, this oil may be delivered through a conduit 38 having a valve 39 to the inlet side of the pump l5 or to any other suitable point in the recirculating cycle of the absorbent oil.

As the vapors pass downward through the bed 23 they are brought into intimate contact with the latter and there is effected a polymerization of undesirable unstable unsaturated hydrocarbon materials to polymer products of higher boiling points. A considerable portion of the latter are withdrawn in the solvent oil removed through the line 34.

The treated vapors pass through a conduit 4| to a cooler 42 where they are condensed. From the cooler 42 the condensate passes through a line 43 to a separator 44 from which aqueous condensate is withdrawn through a valved line 45, while the treated hydrocarbon products are withdrawn through a valved line 46. If desired,

' the latter material may be delivered to storage but in the instance illustrated in Fig. 1, this oil is delivered to a re-run still 41. In the still 41, the light oil is re-distilled to separate it as, completely as may be desired into its constituent parts, and to separate the valuable low-boiling hydrocarbon materials, such as benzol, toluol and xylols, from the higher boiling polymers produced during the refining treatment. The vapors from the still 41 pass through a conventional rectifying column 48 and thence through a vapor line 49 to a condenser 5| and a receiver 52. The various cuts may pass from the latter to separate storage vessels (not shown). The redistillation in the still 41 may be efiected by means of indirect steam, with or without the additional use, if desired, of direct steam, but in any event is conducted in such manner as to leave behind in the still 41 a residue comprising ,the high-boiling polymers, which residue may be withdrawn from the still41 through a valved drain 53. v

In some instances it may be desirable to effect a fractionation of the treated vapors leaving the tower 22 prior to condensation thereof, for the purpose of removing therefrom the polymers formed during the treatment. In Fig. 2 I have illustrated apparatus whereby such fractionation may be eifected'and including also means for removing' entrained low-boiling hydrocarbons from the high-boiling oil removed from the tower 22. 7

Referring now to Fig. 2, the treated vapors, after traversing the bed 23, pass through the vapor line 4| to a fractionating tower 6| of conventional design having plates or trays 82, means for producing reflux such as a cooling coil 63, and a valved steam inlet 64. The high-boiling polymer-containing oil removed from the bottom of the treating tower 22 may in this instance be transferred through a conduit 85 having pump 66 to the fractionating tower 6 I, being introduced thereto at a point above the steam inlet 64 but high-boiling oil, together with the polymers,

passes out of the fractionating tower 6! through a conduit 61 to a separator 68 from which the polymer-containing oil and the aqueous condensate that may be formed are removed through conduits 1| and 12, respectively.

The treated vapors, now freed from polymers, pass through a vapor line 13 to the condenser 42 and water separator 44, as in the instance illustrated in Fig. 1.

It will be understood by those skilled in the art that spent solid adsorbent material may be re moved from the tower 22 and replaced with fresh material whenever desired, and that the spent clay or other adsorptive material may be revivified and re-employed in the tower 22.

As an alternative mode of procedure, the fullers earth or other. adsorbent material may be continuously supplied to and removed irom the ing column similar to the fractionating column- 6I of Fig. 2, but provided with means for introducing and removing the slurry, as well as means for maintaining the desired temperatures.

As indicated hereinabove, it will be obvious to those skilled in the art that thespeciflc instances described hereinabove are intended to be illustrative ratherthan definitive of my invention, which may variously be practiced within the scope of the claims hereinafter made.

What I claim is: g

1. The process of purifying a mixture of hydrocarbon vapors consisting substantially entirely of benzol, toluol and xylols and steam in order to remove unstable unsaturated constituents from said hydrocarbons, which comprises passing said mixture of hydrocarbon vapors and steam through a body of solid adsorbent catalytic material effective to promote polymerization of unstable unsaturated constituents of said vapors to polymers of higher boiling points, and simultaneously passing through said body of adsorbent material a relatively high boiling solvent oil heated to a temperature sufllciently high to mainciency of the adsorbent by removing polymers therefrom.

2. The process of recovering refined hydrocarbons consisting substantially entirely of benzol, toluol and xylols from gases containing such hydrocarbons in a relatively impure state, which comprises scrubbing the gases with a recirculating flow of relatively high-boiling absorbent oil to remove benzol, toluol and xylols therefrom, steam-distilling the thereby enriched absorbent oil during recirculation thereof to remove the absorbed aforementioned hydrocarbons and to produce a mixture of hydrocarbon vapors and steam, passing the mixture of hydrocarbon vapors and steam resulting from said steam-distilling operation through a bed or solid adsorbent catalytic material effective to promote a polymerization or unstable unsaturated hydrocarbon constituents to polymers of higher-boiling points, simultaneously passing through said body of adsorbent material a hydrocarbon solvent oil heated to a temperature sufliciently high to maintain the desirable constituents in said hydrocarbon vapors and said steam during the passage thereof through the catalytic material in vaporous form but below a temperature at which vaporization -of said high boiling solvent takes place, separating the desired treated vapors from said adsorbent material and said solvent, condensing said vapors and adding saidsolvent to said recirculating body of absorbent oil to refresh the latter.

MALVIN R. MANDELBAUM. 20 

